JP2918687B2 - Polyparabanic acid selective separation membrane - Google Patents

Description

The present invention relates to a novel water- and permselective membrane for treating organic substances. More specifically, ultrafiltration (UF), microfiltration (M
F), a membrane for separating and concentrating an organic mixture and a water / organic mixture by a pervaporation (PV) method and a vapor permeation (VP) method.

[Conventional technology]

As a method for separating various aqueous solutions, organic liquid mixtures, and vapor mixtures using a membrane, a reverse osmosis membrane, an ultrafiltration membrane, a dialysis membrane, a dehumidification membrane, and the like have been put to practical use. In recent years, permeation vaporization and vapor permeation have been spotlighted as new separation methods that are not affected by osmotic pressure when separating organic substances.

The range of application of the membrane is expanding to organic solvents and vapors in addition to conventional aqueous and inorganic gases. Examples of the solvent-resistant separation membrane capable of separating such an organic substance mixture include a Teflon-based microfiltration membrane and a polyimide-based separation membrane (JP-A-54-71785).
And the ultrafiltration membrane of JP-A-58-14908 are known.

As membrane materials for pervaporation and vapor permeation separation typified by water / alcohol separation, cellulose-based materials such as cellulose acetate, and aromatic polymers such as polyamide, polysulfone, and polyimide have been studied.

Examples of pervaporation membranes for water / acetic acid separation include copolymerization of acrylic acid and acrylonitrile and copolymerization of acrylic acid and styrene (membrane 10 , p.247 (1985)), ion-crosslinked polyacrylic acid and nylon 6. Blend film (J.Appl.Pol
ym. Sci., 35 , p. 119 (1988)), ion exchange membrane (membrane 13 , 109)
(1988)) and a blend film of polyvinyl alcohol and various vinyl-based hydrophilic polymers (Makromol. Chem., 18 ).
8 , p. 1973 (1987)), but the durability has not been studied, and the separation properties cannot be said to be excellent.

JP-B-58-46323, JP-A-62-45319, JP-A-63-91123, JP-A-63-91124 and JP-A-1-1270
No. 29 discloses a membrane made of polyparabanic acid. U.S. Pat. No. 3,618,591 and Japanese Patent Publication No. 47-19715 disclose polyparabanic acid. JP-A-58-129052 discloses a crosslinkable composition using polyparabanic acid and an organic sulfonic acid or a derivative thereof as a crosslinking agent.

(Disclosure of the present invention)

In the organic substance separation membrane typified by the above-described pervaporation and vapor permeable membrane, the membrane to be used not only has heat resistance to withstand high operating temperatures, but also has sufficient resistance to the target organic substance. is necessary.

In water / ethanol pervaporation separation, an anionic group-containing polysaccharide membrane having high resolving property (Japanese Patent Application Laid-Open No. 60-129104)
JP-A-59-109) and polyvinyl alcohol crosslinked film
It is hard to say that a membrane such as that disclosed in Japanese Patent Publication No. 204) is suitable for a wide range of organic matter separation other than water / alcohol separation in terms of heat resistance and solvent resistance.

An object of the present invention is to not only have a high separation property in the separation of an organic mixture and water / organic substances, but also have a solvent resistance capable of coping with a wide concentration range of an organic substance, and at the same time operating conditions at a high temperature. Another object of the present invention is to obtain a separation membrane that can withstand the above.

[Means for solving the problem]

As a result of intensive studies on the above points, the present invention has been reached. That is, the present invention has a general formula (Where R represents a divalent organic group).

In general, an organic mixture or a membrane for separating water / organic matter is required to have not only excellent selective separation properties but also solvent resistance and heat resistance. The present inventor has selected water / acetic acid as a model of an organic mixture to be separated, and selected a pervaporation method from various separation methods, and searched for a membrane material having excellent durability of separation. As a result, polyparabanic acid was found. Furthermore, as a result of various investigations to improve the separation performance of the membrane indicated by the separation coefficient and the permeation rate, and to impart durability, particularly, blending a polymer containing a sulfonic acid group into the membrane, In addition, the inventors have found that it is effective to thermally crosslink the film, and have completed the present invention. Hereinafter, the present invention will be described in more detail.

The polyparabanic acid in the present invention has the general formula (Where R represents a divalent organic group).

As R (divalent organic group) in the above general formula, a combination of two or more groups is also included in addition to using R alone.

As a specific example, And the like.

The method for producing the polyparabanic acid is not particularly limited, and US Pat. No. 3,661,859, JP-B-47-19715
And Japanese Patent Publication No. 49-12360. Also, European Polymer Journal (Eur. Polym. J., 19 , pp. 143-146 (198
3)) shows a method of synthesizing polyurea and oxalyl chloride by an intramolecular reaction using pyridine as a catalyst. In this case, the inclusion of a partial urea bond in the repeating unit is included in the present invention without departing from the spirit of the present invention.

In order to increase selectivity and improve water permeability during water / organic matter separation, sulfonic acid groups (-SO ₃ M; M forms salts such as H, alkali metals, alkaline earth metals, amines and polycations) It is preferred to blend with a polymer containing (possible ions). Specifically, various polymers partially or wholly sulfonated using, for example, polymers such as polystyrenesulfonic acid and polyethylenesulfonic acid, and sulfonating agents such as chlorosulfonic acid and fuming sulfuric acid (for example, polyphenylene oxide, Sulfonated products such as polysulfone, polyamide and polyurea)
Can be mentioned.

Further, the present polyparabanic acid itself can be sulfonated using a sulfonating reagent and blended, and in this sense, partially sulfonated polyparabanic acid itself is also included in the present invention. The blending ratio of the polyparabanic acid and the sulfonic acid group-containing polymer can be changed according to the separation target. is there.

The polyparabanic acid selective separation membrane according to the present invention preferably has a three-dimensional structure by crosslinking in order to improve the membrane strength and separation performance.

200 ° C or more and 400 ° C or less of the formed film, more preferably
The object can be achieved by heating to a temperature of 250 ° C. or more and 350 ° C. or less, or a glass transition temperature or less to introduce a crosslinked structure.

The membranes prepared in this way can be used in a wide range of organic and water / organic mixtures, for example organic acids such as formic acid, acetic acid, butyric acid, methanol, ethanol, 1-propanol, 2-
Pervaporation separation in systems such as alcohols such as propanol and n-butanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, aldehydes such as acetaldehyde and propionaldehyde, and amines such as pyridine and picoline. (P
V) and vapor permeation separation (VP).

Further, by utilizing the characteristics of the polyparabanic acid selective separation membrane, it can be used as a permselective membrane for treating a wide range of organic substances, water and ions. For this, application to a dialysis membrane, a reverse osmosis membrane, an ultrafiltration membrane, a microfiltration membrane, or the like can be considered. In addition, it can be used as a base film for gas separation, RO, PV, and VP composite membranes, taking advantage of its properties such as excellent heat resistance and solvent resistance.

The membrane according to the present invention can be used in any form of a flat membrane, a tubular membrane, and a hollow fiber membrane. The flat membrane may be laminated as it is, or may be formed into a module by being formed into a pleated shape or a spiral shape. Generally, in order to increase the transmission speed, it is preferable to reduce the film thickness,
For this purpose, it is used in the form of an asymmetric membrane by a technique such as a phase inversion method or a composite membrane by a technique such as coating on a support (substrate membrane).

In gas separation, pervaporation, vapor permeation methods, etc., the separation active layer of an asymmetric membrane or a composite membrane is substantially non-porous with no pores observed by an electron microscope with a magnification of 10,000 times, and the thickness is 10 μm or less. preferable. When used in the form of a hollow fiber, only one of the hollow fibers has a separation active layer, and the other side is microporous (up to 0.1%).
(μm or more) is preferable in order to keep the transmission resistance low.

In a series of separation membranes ranging from RO, UF, MF, it is necessary to change the pore size and thickness of the separation active layer according to the separation target,
By applying a method known so far, a flat membrane, a hollow fiber membrane, or the like can be manufactured from a polymer solution for film formation containing various additives by a phase inversion method or the like. .

〔The invention's effect〕

The polyparabanic acid selective separation membrane according to the present invention not only has excellent separation characteristics for separation of organic substances and water / organic substances, but also has excellent solvent resistance and heat resistance, such as pervaporation and vapor permeation. This is extremely effective for practical use of the membrane separation process.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.

 The separation coefficient was calculated by the following equation.

α = (X / Y) _p / (X / Y) _f where X represents the concentration of water, Y represents the concentration of acetic acid or ethanol, and p and f represent the permeate side and the supply side, respectively.

Example 1 Dimethylformamide was added to a polyparabanic acid solution XT-702 manufactured by Tonen Petrochemical Co., Ltd. (corresponding to the TMF grade of Comparative Example 2) to make a 10 wt% solution, which was cast on a glass plate using an applicator. And a film having a thickness of 17 μm. After vacuum drying at 100 ° C overnight, add 200 ° C
For 6 hours under vacuum. Table 1 shows the water / acetic acid pervaporation performance of this membrane.

Example 2 The film obtained in Example 1 was further heat-treated at 250 ° C. for 2 hours. Table 1 shows the separation performance.

Example 3 The film obtained in Example 1 was further heat-treated at 300 ° C. for 2 hours. This film had undergone thermal crosslinking and was no longer soluble in dimethylformamide. Table 1 shows the separation performance.

Example 4 The following sulfonic acid group-containing polyurea was obtained by reacting equimolar amounts of 2,5-diaminobenzenesulfonic acid and p-phenylenediisocyanate in dimethylformamide.

This polyurea was blended with the polyparabanic acid solution used in Example 1 so as to have a ratio of 8.8% by weight based on the total polymer content in the solution, and cast on a glass plate to form a uniform 18 μm film. I got This film was heat-treated at 100 ° C. overnight and further at 200 ° C. for 6 hours. Table 1 shows the separation performance.

Example 5 The film obtained in Example 4 was further subjected to a heat treatment under vacuum at 250 ° C. for 2 hours. Table 1 shows the separation performance.

Example 6 The film obtained in Example 4 was further subjected to a heat treatment under vacuum at 300 ° C. for 2 hours. This film had undergone thermal crosslinking and was no longer soluble in dimethylformamide. Table 1 shows the separation performance.

Example 7 The polyurea containing a sulfonic acid group used in Example 4 was blended with the polyparabanic acid solution used in Example 1 so as to have a ratio of 16.4% by weight with respect to the total polymer content in the solution. A uniform film was formed in the same manner as in Example 4. 250 of this film
Vacuum dried at 2 ° C. for 2 hours. Table 1 shows the separation performance.

Comparative Example 1 A polyparabanic acid film made mainly of poly (2,4,5-trioxo-1,3-imidazolidinediyl) -1,4-phenylenemethylene-1,4-phenylene and manufactured by Tonen Petrochemical Co., Ltd. Water / acetic acid pervaporation performance was measured using a grade (glass transition temperature 290 ° C.). 80 at 70 ° C for feed
Water was preferentially permeated when measurement was performed using a weight% acetic acid and the degree of vacuum on the secondary side was about 1 mmHg. Table 2 shows the obtained results.
Shown in

Comparative Example 2 Tonen Petrochemical Co., Ltd. mainly comprising poly (2,4,5-trioxo-1,3-imidazolidinediyl) -2,4-tolylene
Separation performance was measured in the same manner as in Comparative Example 1 using a polyparabanic acid film made of TMF grade (glass transition temperature: 350 ° C.). Table 2 shows the results.

Comparative Example 3 The MF grade membrane used in Comparative Example 1 was converted to 80 wt% acetic acid at 60 ° C.
After immersion for 35 days, pervaporation performance of water / acetic acid was compared with Comparative Example 1.
It measured similarly to. Table 2 shows the results.

Comparative Example 4 The TMF grade membrane used in Comparative Example 2 was immersed in 80% by weight acetic acid at 60 ° C. for 51 days. The shape of the film did not change as in the MF grade film. Table 2 shows the separation performance of the film after immersion.

Comparative Example 5 Using the MF grade membrane used in Comparative Example 1, water / ethanol pervaporation separation was performed. 90wt at 60 ℃
% Ethanol was used. Table 2 shows the results.

Comparative Example 6 Using the TMF grade membrane used in Comparative Example 2, Comparative Example 5
The separation performance was measured in the same manner as described above. Table 2 shows the results.

Continuation of the front page (56) References JP-A-1-127024 (JP, A) JP-A-63-91123 (JP, A) JP-A-62-45319 (JP, A) JP-A-53-11884 (JP, A) JP-A-63-91124 (JP, A) JP-A-58-129052 (JP, A) JP-B-58-46323 (JP, B2) JP-B-47-19715 (JP, B1) JP-B Shower 49-12360 (JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) B01D 71/62

Claims (8)

(57) [Claims] (1) General formula (Wherein, R represents a divalent organic group) mainly composed of polyparabanic acid having a repeating unit represented by the following formula: a blend with the polyparabanic acid and a polymer containing a sulfonic acid group, or a repeating unit represented by the above general formula (I). After forming a selective separation membrane made of sulfonic acid group-containing polyparabanic acid, by a pervaporation method or a vapor permeation method, characterized by using a crosslinked polyparabanic acid selective separation membrane obtained by heat-treating the membrane at a temperature of 200 ° C. or more. Organic matter separation and concentration method. 2. The polyparabanic acid of the formula (II) The method for separating and concentrating organic substances according to the pervaporation method or the vapor permeation method according to claim 1, comprising a repeating unit represented by the following formula: 3. The method for separating and concentrating organic substances by a pervaporation method or a vapor permeation method according to claim 1, wherein the sulfonic acid group-containing polymer to be blended is a sulfonated polyurea. 4. General formula (Wherein, R represents a divalent organic group) mainly composed of polyparabanic acid having a repeating unit represented by the following formula: a blend with the polyparabanic acid and a polymer containing a sulfonic acid group, or a repeating unit represented by the above general formula (I). A crosslinked polyparabanic acid selective separation membrane formed by forming a selective separation membrane made of sulfonic acid group-containing polyparabanic acid and then heat-treating the membrane at a temperature of 200 ° C. or higher. 5. The polyparabanic acid of the formula (II) The crosslinked polyparabanic acid selective separation membrane according to claim 4, comprising a repeating unit represented by the following formula: 6. A crosslinked polyparabanic acid selective separation membrane according to claim 4, wherein the sulfonic acid group-containing polymer to be blended is a sulfonated polyurea. 7. A composite membrane comprising a polyparabanic acid base film and a thin film covering the base film, wherein the base film is the crosslinked polyparabanic acid selective separation membrane according to claim 4. . 8. A separation / concentration method using a selective separation composite membrane having a substantially non-porous separation active layer, wherein the composite membrane according to claim 7 is used.